Opinions!!

A great next step, for $400: Jolida (Black Ice)
SS-X Sound Expander!  This piece really has worked
well with my Prodigys.  (Read about them in other
posts)  

Wanting to try domething different?
Why not stay with the speakers you have,
just give yourself more options to tailor what
the Prodigys can do for you!

Most in your situation that have stayed and appreciated panel speakers have a real hard time moving to a boxed speaker. ’m surprised you didn’t put Soundlab on your list.  They would check all your boxes.

Happy to note that the MBL's got a mention at least....pricey....

Wide soundstage, go omni.  A pair of boxes can only take you so far.

I've a pair of Walsh roughly a third of the way into a space.

'Soundstage' becomes as large as I care to make it.

I would be interested in that comparison.

Check out the Dali Rubicon 8's for a large room..I have the 6's in my mid size room and they could go in a larger room to a point, but the 8's would totally be comfortable. Wide soundstage, bass is off the hook and the ribbon tweeters are smooth and sweet..no edge anywhere.

Thanks for all the input. Really appreciate it.
It looks like its down to Magico a5 and Persona 9h. Will let you guys know.

If you are looking for a big, wide soundstage, the DeVore Gibbon Xs would be another to consider.  

Joseph Audio Perspective2 is another fantastic option (or even the Pearl 20/20 if budget permits).

I agree with Rodman99999 - stick with electrostatics / planer speakers- I compared my Maggie 1.7i to Martin Logan and stuck with my Maggies- better sound stage. I do not know your price range - but the Maggie 1.7i are only $2,200 new. The Maggie 3.7i are $6,500 new. Everyone complains about the base lacking below 50 hertz with Maggies - solution - add The Swarm (4 subwoofer array and the system comes with it's own Amp) - got a TAS Golden Ear award twice - cost $3,200.  This set up is worth investigating - especially in your large room.  

Just my two cents - Happy Listening

@b_limo  had an interesting suggestion. FWIW, this interview with MBL might add to your understanding of their approach: https://parttimeaudiophile.com/2020/08/06/a-deep-dive-in-the-high-end-sitting-down-with-mbl/

I too used the ML Prodigy. They sound better bi-amped with an active crossover. Better yet are the Quad 2905’s. I have owned two pairs of 2905’s and one pair of 2805’s for ten years or more, and am just experiencing my first failures. One panel has gone (out of 32) and one high voltage transformer.

If you don’t use them like sonic bludgeons they seem to work fine - at least, mine do. Once you’ve lived with ESL’s, I don’t think there is any going back. One highly respected member here owns MBL’s and he opined that they were better than anything but ESL’s.

If you like the ESL sound, stay with it, I say.

@bbenzaquen6343- I’ve found both Kimber Selects (KS-1130 & 1030) and Synergistic Research (Tesla Apex & Analogue Tricon), to pass whatever determines accurate ambience retrieval, without hindrance.      I’ve no doubt; their later iterations would be even better, in some ways.

Could try OB’s. PureAudioProject Quintets, Trios, Jump in at any size. Upgradable without loss of investment, efficient, Just ask VPI, Whammerdyne, and more that use them to demo their own products. Says a lot. Once heard, not easily forgotten. 

How about these?  I think quite a few people really love them.  They are possibly the most impressive speaker that I’ve ever heard.  

https://www.audiogon.com/listings/lisa63a0-mbl-101-e-mk1-full-range?refsource=hifishark

@topfinadv, Please read this review of the NSMT Model 100, it plays to your main criterion of soundstage;  https://6moons.com/audioreview_articles/nsmt/     Manufacturer website;  https://nsmt-loudspeakers.com/

@rodman99999 what interconnects would you recommend ?

consider spatial audio if you want to avoid tradiitional box speakers - they are quite outstanding

also, i would note all speakers on your list have a ’lively’ presentation, system matching important unless you like a live-sounding, sometimes aggressive sound...  don't remove that arc sp-6e!!

Most importantly I am looking for a detailed wide soundstage

Number one comment I get, they are always impressed with the detailed wide (and deep) sound stage. The last group who were here, we played Aja, said it was the best he ever heard. Tekton Moab. But hey, don’t just take our word for it, https://youtu.be/7RxRTFx6Cd0?t=350 That's Double Impacts he's talking about. Moabs have that in spades. Ulfberht even that much better. In the price range you are talking? Ulf, totally.

A lot of guys say this is what they want. Then they go buy a Faberge Egg for five times as much. Tekton will never be featured in Architectural Digest. If this is a deal breaker for you, oh well.

^^^    Then stick with electro-statics, magnetic-planars or open baffles (ie: Spatial Audio Lab).     Your interconnects can also make or break an accurate recovery of ambience info.      Of course; everything else matters, too.

Most importantly I am looking for a detailed wide soundstage

What kind of things are you looking for and/or would like to improve upon over your MLs, and what aspects of speaker performance and sound reproduction are most important to you?

I'm using a pair of persona 7f that I grabbed instead of the blades because they were within driving distance. I think if you've been listening to Martin Logans for the last decade you're going to find most conventional speakers dull, that said the personas are the most detailed without being sibilant. detail is this speakers description top to bottom, bass, mids, and treble. even imaging and soundstage is exposed, really impressive and the big ones are on sale here for what looks like 1/2 price used. 

I have all the above speakers on my list also but I think at this point neither is better, only different. 

The Yamaha NS-5000's would be perfect for that set-up and room.